I should have mentioned the myriad events planned by the city of Philadelphia in celebration of the Independence Day holiday. Here is the site with the listings of events: www.americasbirthday.com/eventlistings.asp

Be sure to check the listings under EVERY date, because some of the events run for multiple days but are only listed under the starting date (with a note that says something like "daily through July 4th", for example).

And THEN there are the many museums in town (I don't know if your friend is interested in that). The Philadelphia Museum of Art is the most well-known, thanks to the Rocky movie (and no, the Rocky statue is NOT permanently displayed at the top of the museum steps, though the debate rages on over whether it should be). My personal fave is the Rodin Museum (you know, the guy who sculpted "The Thinker"), which is down the parkway from the Philly Museum. If your friend's intrigued by archaeology, then the University of Pennsylvania Museum is the place to go. Here are two good lists of area museums:

One

Two

Neither lists the most bizarre one around:
The Mercer Museum in Doylestown, PA (plus nearby Fonthill, the home of the guy who built the Mercer Museum). Both are early examples of reinforced-concrete construction, both designed by the eccentric Henry Chapman Mercer, and both are really strange. Fonthill was featured on the A&E channel series "America's Castles" and has long been nicknamed "the concrete castle". Mercer housed his collection of folk art and 19th century artifacts in the museum, and the structure is as interesting as its contents if not more so. A must-see for any fan of weird Americana.